WMV (Windows Media Video) is a file type which can contain video, audio and subtitles including closed captioning) in one of several video compression formats developed by Microsoft. WMV was originally designed for Internet streaming applications as a competitor to RealVideo. Other formats, such as WMV Screen and WMV Image, cater for specialized content. Through standardization from the Society of Motion Picture and Television Engineers (SMPTE), WMV 9 has gained adoption for physical-delivery formats such as HD DVD and Blu-ray Disc. The first version of the format, WMV 7, was introduced in 1999, and was built upon Microsoft’s implementation of MPEG-4 Part 2.

A WMV file is in most circumstances encapsulated in the Advanced Systems Format (ASF) container format. The file extension .wmv describes ASF files that use Windows Media Video. Microsoft recommends that ASF files containing non-Windows Media formats use the generic .asf file extension.

Although WMV is generally packed into the ASF container format, it can also be put into the Matroska or AVI container format. The resulting files have the .mkv and .avi file extensions, respectively. One common way to store WMV in an AVI file is to use the WMV 9 Video Compression Manager (VCM) codec implementation.

Software that can play WMV files includes Windows Media Player, RealPlayer, Mplayer, Media Player Classic, VLC Media Player and K Multimedia Player. The Microsoft Zune media management software supports the WMV format, but uses a Zune-specific variation of Windows Media DRM which is used by PlaysForSure. Many third-party players exist for various platforms such as Linux that use the Ffmpeg implementation of the WMV format. Flip4Mac WMV is a third-party QuickTime component which allows Macintosh users to play WMV files in any player that uses the QuickTime framework, free of charge to view files but chargeable to convert formats. All of these formats make possible saving of filmed material, useful for such purposes as archiving and transcription.

Software that exports video in WMV format include CyberLink PowerDirector, Avid (PC version), Windows Movie Maker, Windows Media Encoder, Microsoft Expression Encoder, Sorenson Squeeze, Sony Vegas Pro, Adobe Premiere Pro, Adobe After Effects, AVS Video Editor, Telestream Episode, Total video converter and Telestream FlipFactory. Programs that encode using the WMV Image format include Windows Media Encoder, AVS Video Editor and Photo Story.

The ASF container format, in which a WMV stream may be encapsulated, can. Windows Media DRM (digital rights management), which can be used in conjunction with WMV, supports time-limited subscription video services such as those offered by CinemaNow. Windows Media DRM, a component of PlaysForSure and Windows Media Connect, is supported on many portable video devices and streaming media clients such as the Xbox 360.